Multilayer card

Abstract
A multilayer card is described. The multilayer card includes a base layer, a watermark layer, an image layer, and an opaque layer. The watermark layer is provided on the base layer and is at least partially transparent. The image layer is provided on the watermark layer. The opaque layer is provided on the image layer.
Description




BACKGROUND OF THE INVENTION




The present invention relates to multilayer cards, and more specifically, to multilayer cards and methods of manufacturing the multilayer cards.




Various identification cards have been used for identifying individuals. Those identification cards have some security marks or prints in order to avoid counterfeiting. Furthermore, identification cards usually have to be protected against tampering on the surfaces of the cards. For example, some cards are covered by a transparent plastic film for surface protection.




In the prior art, a printer such as a thermal transfer printer prints images on a base material of such an identification card first. Then, the process of covering the card by a film is performed after printing. Therefore, the prior art requires two separate steps for making laminated tamper-proof cards: a printing step and a laminating step. However, this two-step manufacturing technique poses some problems. Since the printing step and the laminating step are performed by totally different mechanisms, it is difficult to easily incorporating two functions into a single machine. As a result, providing a printer which outputs tamper-proof, printed cards becomes economically unrealistic especially for personal use.




In view of these and other issues, it would be desirable to have a technique allowing a thermal transfer printer to print an identification card and then apply a tamper-proof layer on the card.




SUMMARY OF THE INVENTION




According to various embodiments of the present invention, a multilayer card has a base layer, a watermark layer, an image layer, and an opaque layer. The watermark layer is provided on the base layer, and is at least partially transparent. The image layer is provided on the watermark layer. The opaque layer is provided on the image layer. The opaque layer functions as a protective layer against tampering or scratching.




In some embodiments, the opaque layer includes a metallic layer.




In some specific embodiments, the opaque layer includes a regular color layer.




A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.











BRIEF DESCRIPTION OF THE DRAWING




The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:





FIG. 1

is a cross-sectional view of a thermal transfer printer for manufacturing a specific embodiment of a multilayer card according to the present invention.





FIG. 2

is a cross-sectional view of an alternative thermal transfer printer for manufacturing the multilayer card according to the present invention.





FIG. 3

is a cross-sectional view of a specific example of the ink film used for the embodiments of the multilayer card and the method of manufacturing the multilayer card according to the present invention described referring to

FIGS. 1 and 2

.





FIG. 4

is a cross-sectional view of a multilayer card of a specific embodiment according to the present invention during the printing process.





FIG. 5

is a cross-sectional view of the multilayer card of a specific embodiment according to the present invention after the printing process.





FIG. 6

is a cross-sectional view of a multilayer card of an alternative embodiment according to the present invention.





FIG. 7

is a cross-sectional view of a multilayer card of another specific embodiment according to the present invention.





FIG. 8

is a cross-sectional view of a specific example of the base layer film used for the embodiments of the multilayer card and the method of manufacturing the multilayer card according to the present invention described referring to FIGS.


1


and


2


.











DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS




Various embodiments of the present invention will now be described in detail with reference to the drawings, wherein like elements are referred to with like reference labels throughout.




Various embodiments of the present invention have a base layer, a watermark layer, an image layer, and an opaque layer. The opaque layer functions as a protective layer against tampering or scratching.





FIG. 1

is a cross-sectional view of a thermal transfer printer


100


for manufacturing a specific embodiment of a multilayer card according to the present invention. The thermal transfer printer


100


includes a roller printing section


102


, a thermal transfer printing section


104


, and a controller


106


within a housing


108


. A printing medium


110


is fed along a medium flow path


112


from left to right in FIG.


1


.

FIG. 1

shows three locations of the printing medium


110


in the thermal transfer printer


100


.




Suitable polymers for the printing medium


110


include polyvinylchloride (PVC), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polypropylene sulfate (PPS), and polyethylene terephthalate glycol (PETG). Circles shown in

FIG. 1

represent rollers or platens, and elongated rectangulars


110


in

FIG. 1

represent cards or plate-like materials used as the printing medium


110


.




The roller printing section


102


includes a transfer roller


120


which is operable to heat opaque ink on an ink film


122


, thereby transferring the opaque ink from the ink film


122


to the printing medium


110


. In order to heat the opaque ink, the transfer roller


120


has a heater


124


therein. In order to apply pressure to the ink film


122


and the printing medium


110


, the transfer roller


120


is mechanically coupled to a pressure mechanism


126


which presses the transfer roller


120


against a platen


128


. The pressure mechanism


126


includes, for example, a spring. Thus, the transfer roller


120


presses the ink film


122


and the printing medium


110


against the platen


128


. The ink film


122


includes at least one of a gold color layer, a silver color layer, and a bronze color layer on a base film. The base film is made from plastic materials including polyethylene terephthalate (PET).




The platen


128


included in the roller printing section


102


in this specific embodiment is a roller having a rubber layer thereon. However, the platen


128


may be any other suitable type of platen including a flat platen. Feeding rollers


130


and


132


feed the printing medium


110


onto the transfer roller


120


and the platen


128


along the medium flow path


112


. The controller


106


controls rotational speeds and directions of the transfer roller


120


and the feeding roller


130


appropriately.




The thermal transfer printing section


104


is operable to heat regular color ink on a regular color ink film


140


for transfer the regular color ink from the regular color ink film


140


to the printing medium


110


. The regular color ink film


140


includes at least one of a cyan color layer, a magenta color layer, a yellow color layer, a black color layer, and a white color layer on a base film. The base film is made from plastic materials including polyethylene terephthalate (PET).




The thermal transfer printing section


104


includes a printing head


142


having a plurality of resistance heating elements


144


, and a platen


146


. The resistance heating elements


144


apply heat to the regular color ink film


140


based on electric drive pulses representing image data. The printing head


142


presses the regular color ink film


140


and an intermediate transfer film


148


against the platen


146


, thereby transferring the regular color ink to the intermediate transfer film


148


by heat and pressure. The intermediate transfer film


148


constitutes a closed loop, which rotates counterclockwise in

FIG. 1

supported by feeding rollers


150


,


152


,


154


and


156


.




The regular color ink transferred from the regular color ink film


140


to the intermediate transfer film


148


is carried counter clockwise to a point where an intermediate transfer roller


158


and a platen


160


contact the printing medium


110


. In order to determine the exact position of the printing medium


110


, the thermal transfer printing section


104


includes a sensor


162


which detects a predetermined point on the printing medium


110


by utilizing, for example, an optical sensing technique. Feeding rollers


164


and


166


feed the printing medium


110


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The controller


106


controls rotational speeds and directions of the feeding roller


164


appropriately.




The printing medium


110


is positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. Then, the feeding rollers


164


and


166


feed the printing medium


110


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The intermediate transfer roller


158


presses the intermediate transfer film


148


and the printing medium


110


against the platen


160


, thereby transferring the regular color ink from the intermediate transfer film


148


to the printing medium


110


by pressure. Feeding rollers


170


and


172


feed the printing medium


110


out of the housing


108


of the thermal transfer printer


100


along the medium flow path


112


. The controller


106


controls rotational speeds and directions of the feeding rollers


170


and


172


appropriately.





FIG. 2

is a cross-sectional view of an alternative thermal transfer printer


200


for manufacturing the multilayer card according to the present invention. The thermal transfer printer


200


includes the roller printing section


102


, a thermal transfer printing section


204


, and the controller


106


within the housing


108


. The differences between the embodiments shown in

FIGS. 1 and 2

mainly reside in the thermal transfer printing section


204


. Thus, it should be appreciated that elements in

FIG. 2

which are assigned the same reference labels as shown in

FIG. 1

have the same functionalities as those of

FIG. 1

with the exception that the elements are designed to be coordinated with the thermal transfer printing section


204


.




The thermal transfer printing section


204


is operable to heat regular color ink on a regular color ink film


240


for transfer the regular color ink from the regular color ink film


240


to the printing medium


110


. The regular color ink film


240


includes at least one of a cyan color layer, a magenta color layer, a yellow color layer, a black color layer, and a white color layer on a base film, which is made from plastic materials including PET.




The thermal transfer printing section


204


includes a printing head


242


having a plurality of resistance heating elements


244


, and a platen


246


. The resistance heating elements


244


apply heat to the regular color ink film


240


based on electric drive pulses representing image data. The printing head


242


presses the regular color ink film


240


and the printing medium


110


against the platen


246


, thereby transferring the regular color ink from the regular color ink film


240


to the printing medium


110


by heat and pressure.




In the above-described embodiments referring to

FIGS. 1 and 2

, the transfer roller


120


is positioned upstream relative to the thermal transfer printing sections


104


and


204


along the medium flow path


112


of the printing medium


110


. Such an arrangement may be desirable where, for example, the opaque ink on the ink film


122


is printed on the printing medium


110


first, and then the regular color ink on the regular color ink films


140


and


240


is printed on the printing medium


110


since the thermal transfer printers


100


and


200


can efficiently print the opaque ink as a background layer on the whole surface of one side of the printing medium


110


.





FIG. 3

is a cross-sectional view of a specific example of the ink film


122


used for the embodiments of the multilayer card and the method of manufacturing the multilayer card according to the present invention described referring to

FIGS. 1 and 2

. The ink film


122


includes a base film


300


, an adhesive layer


302


, and an opaque color layer


304


. The base film is made from plastic materials such as PET. The adhesive layer


302


is interposed between the base film


300


and the opaque color layer


304


for affixing the opaque color layer


304


to the base film


300


. The opaque color layer


304


includes at least one of “regular color layers” and “metallic layers.”




In this specification, “metallic ink” includes any ink which includes metallic substance such as metallic powder, metallic film or the like. Thus, the metallic ink includes, for example, gold color ink, silver color ink, and bronze (or copper) color ink. Similarly, a “metallic layer” includes any layer which carries metallic ink thereon. Thus, the metallic layer includes metallic substance such as metallic powder, metallic film or the like. “Regular color ink” means any ink other than the metallic ink, which includes, for example, cyan ink, magenta ink, yellow ink, black ink, and white ink. A “regular color layer” includes any layer which carries regular color ink thereon.





FIG. 4

is a cross-sectional view of a multilayer card


400


of a specific embodiment according to the present invention during the printing process. Before the printing process utilizing the thermal transfer printers


100


and


200


, the multilayer card


400


includes only the printing medium


110


. The specific embodiment of the method according to the present invention will now be described referring to

FIGS. 1

,


4


and


5


.




First, the thermal transfer printer


100


receives the multilayer card


400


from an opening provided on the housing


108


. The feeding rollers


130


and


132


feed the multilayer card


400


onto the transfer roller


120


and the platen


128


along the medium flow path


112


. Next, the transfer roller


120


transfers the opaque color layer


304


from the ink film


122


to an upper surface of the printing medium


110


of the multilayer card


400


. A transferred opaque color layer


404


is affixed to the printing medium


110


by heat and pressure which are applied by the transfer roller


120


, the heater


124


, and the platen


128


. Then, an adhesive layer


406


is applied to a surface of the transferred opaque color layer


404


for improving adhesiveness between the transferred opaque color layer


404


and regular color layers printed on the transferred opaque color layer


404


.





FIG. 5

is a cross-sectional view of the multilayer card


400


of the specific embodiment according to the present invention after the printing process. After printing the opaque color layer


404


, the feeding rollers


164


and


166


feed the multilayer card


400


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The multilayer card


400


is positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. Then, the feeding rollers


164


and


166


feed the multilayer card


400


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The intermediate transfer roller


158


presses the intermediate transfer film


148


and the multilayer card


400


against the platen


160


, thereby transferring a cyan color layer


502


, a magenta color layer


504


, a yellow color layer


506


, a black color layer


508


, and a white color layer


510


from the intermediate transfer film


148


to a surface of the adhesive layer


406


. The order of printing the regular color layers may be modified appropriately. It should be appreciated that one or more layers among the cyan color layer


502


, the magenta color layer


504


, the yellow color layer


506


, the black color layer


508


, and the white color layer


510


may be omitted to be printed on the multilayer card


400


.




The specific embodiment of the method according to the present invention described above referring to

FIGS. 1

,


4


and


5


can be implemented by utilizing the thermal transfer printer


200


illustrated in

FIG. 2

in a similar manner except that the regular color printing is performed by the thermal transfer printing section


204


rather than the thermal transfer printing section


104


. Thus, further detail is omitted.




In the specific embodiments described above, the regular color printing by the thermal transfer printing sections


104


and


204


can be implemented by a single thermal head. However, it should be appreciated that a plurality of thermal heads can be used for the regular color printing.





FIG. 6

is a cross-sectional view of a multilayer card


600


of a specific embodiment of the present invention. Now referring to

FIGS. 1

,


2


and


6


, a specific embodiment of the method for manufacturing a multilayer card according to the present invention will be described. This specific embodiment of the invention utilizes one of the thermal transfer printers


100


and


200


. Before the printing process utilizing the thermal transfer printers


100


and


200


, the multilayer card


600


includes only a base layer


602


which corresponds to the printing medium


110


in

FIGS. 1 and 2

.




First, the thermal transfer printer


100


receives the multilayer card


600


from an opening provided on the housing


108


. The feeding rollers


130


and


132


feed the multilayer card


600


through the transfer roller


120


and the platen


128


along the medium flow path


112


. The multilayer card


600


is positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. Then, the feeding rollers


164


and


166


further feed the multilayer card


600


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The thermal transfer printing section


104


transfers a watermark layer


604


from the intermediate transfer film


148


to the multilayer card


600


. The watermark layer


604


is at least partially transparent and thus functions as a watermark for avoiding counterfeiting. The watermark layer


604


includes at least one of an ultraviolet (UV) ink layer, a holographic layer, and a special ink layer for improved security.




Second, the multilayer card


600


is again positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. The feeding rollers


164


and


166


feed the multilayer card


600


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. On top of the watermark layer


604


, the thermal transfer printing section


104


transfers an image layer


606


from the intermediate transfer film


148


to the multilayer card


600


. The image layer


606


includes at least one of the metallic ink and the regular color ink as described above in connection with the opaque color layer


304


, by which various images including characters and graphics are represented.




Then, the feeding rollers


130


,


132


,


164


and


166


feed the multilayer card


600


back onto the transfer roller


120


and the platen


128


along the medium flow path


112


. The transfer roller


120


transfers the opaque layer


304


from the ink film


122


to a top surface of the image layer


606


of the multilayer card


600


. The opaque layer


304


is affixed to the multilayer card


600


by heat and pressure which are applied by the transfer roller


120


, the heater


124


, and the platen


128


. A transferred opaque layer


608


includes at least one of metallic color layers and regular color layers, thereby functioning as a background layer on which the image layer


606


is printed.




Finally, the multilayer card


600


shown in

FIG. 6

is moved along the medium flow path


112


from left to right in FIG.


1


through the feeding rollers


164


,


166


,


170


and


172


for ejection from the housing


108


of the thermal transfer printer


100


.




The specific embodiment of the present invention described above referring to

FIGS. 1 and 6

can be implemented by utilizing the thermal transfer printer


200


illustrated in

FIG. 2

in a similar manner except that the regular color printing is performed by the thermal transfer printing section


204


rather than the thermal transfer printing section


104


. Thus, further detail is omitted.




In the specific embodiments described above, the image layer printing by the thermal transfer printing sections


104


and


204


can be implemented by a single thermal head. However, it should be appreciated that a plurality of thermal heads can be used for the regular color printing.





FIG. 7

is a cross-sectional view of a multilayer card


700


of another specific embodiment of the present invention. Now referring to

FIGS. 1

,


2


and


7


, another specific embodiment of the method for manufacturing a multilayer card according to the present invention will be described. This specific embodiment of the invention utilizes one of the thermal transfer printers


100


and


200


. In this embodiment, further printing on the multilayer card


600


is performed utilizing one of the thermal transfer printers


100


and


200


.




After the printing process described referring to

FIGS. 1

,


2


and


6


is finished, the multilayer card


600


is retained within the housing


108


without ejection from the housing


108


.




First, the multilayer card


600


, i.e., a lower part of the multilayer card


700


is positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. The feeding rollers


164


and


166


feed the multilayer card


700


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. On top of the opaque layer


608


, the thermal transfer printing section


104


transfers an image layer


702


from the intermediate transfer film


148


to the multilayer card


700


. The image layer


702


includes at least one of the metallic ink and the regular color ink as described above in connection with the opaque color layer


304


, by which various images including characters and graphics are represented.




Second, the feeding rollers


130


,


132


,


164


,


166


,


170


and


172


feed the multilayer card


700


back to the sensor


162


. The multilayer card


700


is positioned on a predetermined point on the medium flow path


112


by using the sensor


162


and the feeding roller


164


controlled by the controller


106


. Then, the feeding rollers


164


and


166


further feed the multilayer card


600


onto the intermediate transfer roller


158


and the platen


160


along the medium flow path


112


. The thermal transfer printing section


104


transfers a watermark layer


704


from the intermediate transfer film


148


to the multilayer card


700


. The watermark layer


704


is at least partially transparent and thus functions as a watermark for avoiding counterfeiting. The watermark layer


704


includes at least one of an ultraviolet (UV) ink layer, a holographic layer, and a special ink layer for improved security.




Then, the feeding rollers


130


,


132


,


164


,


166


,


170


and


172


again feed the multilayer card


700


back onto the transfer roller


120


and the platen


128


along the medium flow path


112


. The transfer roller


120


carries a base layer film


822


instead of the ink film


122


.

FIG. 8

is a cross-sectional view of a specific example of the base layer film


822


used for the embodiments of the multilayer card and the method of manufacturing the multilayer card according to the present invention described referring to

FIGS. 1 and 2

. The base layer film


822


includes the base film


300


, the adhesive layer


302


, and a base layer


706


. The base film


300


is made from plastic materials such as PET. The adhesive layer


302


is interposed between the base film


300


and the base layer


706


for affixing the base layer


706


to the base film


300


.




The transfer roller


120


transfers the base layer


706


to a top surface of the watermark layer


704


of the multilayer card


700


. The base layer


706


is affixed to the multilayer card


700


by heat and pressure which are applied by the transfer roller


120


, the heater


124


, and the platen


128


.




Finally, the multilayer card


700


shown in

FIG. 7

is moved along the medium flow path


112


from left to right in FIG.


1


through the feeding rollers


164


,


166


,


170


and


172


for ejection from the housing


108


of the thermal transfer printer


100


.




The specific embodiment of the present invention described above referring to

FIGS. 1 and 7

can be implemented by utilizing the thermal transfer printer


200


illustrated in

FIG. 2

in a similar manner except that the regular color printing is performed by the thermal transfer printing section


204


rather than the thermal transfer printing section


104


. Thus, further detail is omitted.




In the specific embodiments described above referring to

FIGS. 6 and 7

, the base layer


602


corresponding to the printing medium


110


, and the base layer


706


are made from substantially transparent materials including suitable polymers such as PVC, PC, ABS, PPS and PETG. Alternatively, the base layers


602


and


706


may be semi-transparent so that at least part of the image layers


606


and


702


can be seen from the sides of the base layers


602


and


706


, respectively.




In the specific embodiments described above referring to

FIGS. 6 and 7

, the opaque layer


608


is made from materials including resin, cellulose, and ceramics. The opaque layer


608


is not substantially transparent, and functions as a substantially continuously and solidly filled background against which images on the image layers


606


and


702


can be seen. In some embodiments, the thickness of the opaque layer


608


ranges from about 3 μm to about 10 μm, and the thickness of the base layers


602


and


706


ranges from about 0.5 mm to about 1.0 mm.




As described above referring to

FIGS. 6 and 7

, the base layer


602


and the opaque layer


608


are capable of protecting the watermark layer


604


and the image layer


606


, and the base layer


706


and the opaque layer


608


are capable of protecting the watermark layer


704


and the image layer


702


. Thus, a specific embodiment of the multilayer card of the present invention is advantageous especially when tamper-proof and/or scratch-proof cards are necessary. Furthermore, such a specific embodiment is advantageous to enable a user to see the watermark layer


604


and the image layer


606


through the base layer


602


, and to see the watermark layer


704


and the image layer


702


through the base layer


706


.




The card


600


in

FIG. 6

provides an image and watermark on one side of the opaque layer


608


. By printing the watermark and image directly on the base layer


602


and printing the opaque layer


608


on the image layer


606


, this embodiment may provide a more tamper proof card. The card


700


in

FIG. 7

may provide base layers, watermarks, and images on two sides of the opaque layer


608


, which may provide a card that may be even more difficult to counterfeit.




In the specific embodiments described above, the image layer printing by the thermal transfer printing sections


104


and


204


can be implemented by a single thermal head. However, it should be appreciated that a plurality of thermal heads can be used for the regular color printing. For example, five separate thermal heads can be used for five colors (e.g., cyan, magenta, yellow, and black and white) for the thermal transfer printing sections


104


and


204


.




In the above-described thermal transfer printer used for the embodiment of a multilayer card according to the present invention described referring to

FIGS. 1 and 2

, the feeding rollers


130


,


132


,


164


,


166


,


170


and


172


are appropriately positioned along the medium flow path


112


so that the position of the printing medium


110


is controlled to go back and forth along the medium flow path


112


based on a specific printing process (e.g., watermark layer printing, image layer printing, and opaque layer printing) which is applied to the printing medium


110


.




In the above examples of the thermal transfer printer used for the multilayer card according to the present invention described referring to

FIGS. 1 and 2

, the controller


106


can be implemented by any combination of software and/or hardware. For example, the controller


106


can be implemented by a microprocessor, a memory device which stores instruction codes and data, and an interface which drives external devices such as the feeding rollers, the transfer roller, and the intermediate transfer roller.




Although only a few embodiments of the present invention have been described in detail, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. For example, although the illustrated embodiments have been described primarily in the context of a multilayer card, it should be appreciated that various shapes of materials may be used for embodiments of the multilayer card and the method for manufacturing the multilayer card according to the present invention. Therefore, it should be apparent that the above described embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.



Claims
  • 1. A multilayer card, comprising:a base layer; a watermark layer provided on the base layer, the water mark layer being at least partially transparent; an image layer provided on the watermark layer; and an opaque layer provided on the image layer, wherein the opaque layer includes a metallic layer, and wherein the watermark layer and the image layer are formed by transferring ink of an ink film using a thermal transfer printer.
  • 2. The multilayer card of claim 1, wherein the watermark layer includes ultraviolet ink.
  • 3. The multilayer card of claim 1, wherein the watermark layer includes a holographic layer.
  • 4. The multilayer card of claim 1, wherein the base layer is substantially transparent; the watermark layer is printed on the base layer; the image layer is printed on the watermark layer; and the opaque layer is printed on the image layer.
  • 5. The multilayer card of claim 1, further comprising:another image layer provided on the opaque layer; another watermark layer provided on the another image layer, the another watermark layer being at least partially transparent; and another base layer provided on the another watermark layer.
  • 6. The multilayer card of claim 5, wherein at least one of the watermark layer and the another watermark layer includes ultraviolet ink.
  • 7. The multilayer card of claim 5, wherein at least one of the watermark layer and the another watermark layer includes a holographic layer.
  • 8. The multilayer card of claim 5, wherein the opaque layer includes a metallic layer.
  • 9. The multilayer card of claim 5, wherein the base layer is substantially transparent; the watermark layer is printed on the base layer; the image layer is printed on the watermark layer; and the opaque layer is printed on the image layer.
US Referenced Citations (5)
Number Name Date Kind
4629215 Maurer et al. Dec 1986 A
4856857 Takeuchi et al. Aug 1989 A
5449200 Andric et al. Sep 1995 A
5753352 Vanmaele et al. May 1998 A
6268058 Tahon et al. Jul 2001 B1
Foreign Referenced Citations (1)
Number Date Country
08-224982 Sep 1996 JP